package com.knight.hadoop.day03.bigdata.zkDisLock;

import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

public class DistributedClient {
	// 超时时间
	private static final int SESSION_TIMEOUT = 5000;
	// zookeeper server列表
	private static final String connectString = "hadoop3:2181,hadoop4:2181,hadoop5:2181";
	private String groupNode = "locks";
	private String subNode = "sub";

	private ZooKeeper zk;
	// 当前client创建的子节点
	private String thisPath;
	// 当前client等待的子节点
	private String waitPath;

	private CountDownLatch latch = new CountDownLatch(1);

	/**
	 * 连接zookeeper
	 * 
	 * @throws Exception
	 */
	public void connectZookeeper() throws Exception {
		zk = new ZooKeeper(connectString, SESSION_TIMEOUT, new Watcher() {

			@Override
			public void process(WatchedEvent event) {
				// 建立连接的时候，打开latch，唤醒wait在该latch上的线程
				if (event.getState() == KeeperState.SyncConnected) {
					System.out.println("连接事件");
					latch.countDown();
					// 发生了删除事件，且删除的path是waitPath
				} 
				if (event.getType() == EventType.NodeDeleted && event.getPath().equals(waitPath)) {
					try {
						System.out.println("删除事件");
						doSomething();
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			}
		});

		latch.await();

		// 创建子节点
		thisPath = zk.create("/" + groupNode + "/" + subNode, null, Ids.OPEN_ACL_UNSAFE,
				CreateMode.EPHEMERAL_SEQUENTIAL);
		
		System.out.println("创建子节点成功，节点名称："+thisPath);
		
		// wait一小会, 让结果更清晰一些
		Thread.sleep(10);

		// 注意, 没有必要监听"/locks"的子节点的变化情况
		List<String> childrenNodes = zk.getChildren("/" + groupNode, false);

		// 列表中只有一个子节点, 那肯定就是thisPath, 说明client获得锁
		if (childrenNodes.size() == 1) {
			System.out.println("childrenNodes.size()==1 doSomething");
			doSomething();
		} else {
			String thisNode = thisPath.substring(("/" + groupNode + "/").length());
			// 排序
			Collections.sort(childrenNodes);
			int index = childrenNodes.indexOf(thisNode);
			if (index == -1) {
				// never happened
			} else if (index == 0) {
				System.out.println("index==0 doSomething,path: "+thisPath);
				// inddx == 0, 说明thisNode在列表中最小, 当前client获得锁
				doSomething();
			} else {
				// 获得排名比thisPath前1位的节点
				this.waitPath = "/" + groupNode + "/" + childrenNodes.get(index - 1);
				// 在waitPath上注册监听器, 当waitPath被删除时, zookeeper会回调监听器的process方法
				zk.getData(waitPath, true, new Stat());
			}
		}

	}

	private void doSomething() throws Exception {
		try {
			System.out.println("gain lock: " + thisPath);
			Thread.sleep(2000);
			// do something
		} finally {
			System.out.println("finished: " + thisPath);
			// 将thisPath删除, 监听thisPath的client将获得通知
			// 相当于释放锁
			zk.delete(this.thisPath, -1);
		}

	}
	
    public static void main(String[] args) throws Exception {
        for (int i = 0; i < 10; i++) {
            new Thread() {
                public void run() {
                    try {
                        DistributedClient dl = new DistributedClient();
                        dl.connectZookeeper();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }.start();
        }

        Thread.sleep(Long.MAX_VALUE);
    }


}
